The present invention relates generally to monitoring and control of the operation of a hydroelectric power generation facility. In particular, the invention relates to a technique for continuous evaluation of hydraulic performance costs and facility maintenance costs associated with operation of a turbine power generating installation in terms useful to operations, engineering and management personnel.
Various control and monitoring systems have been proposed and are currently available for regulating operation of hydroelectric power production facilities. Such systems are typically dedicated to a particular facet of plant operation, or may more broadly group a number of control systems into a centralized control scheme. It is also known in the art of hydroelectric plant management to determine certain optimal or desired levels of operation, such as gate and blade positions of a Kaplan-type turbine, that are believed to be the best attainable levels for maximizing hydraulic efficiency given the plant technology, environmental constraints and so forth. However, it is also common that a particular facility may not be capable of continuously maintaining the desired levels of key operating parameters. For example, equipment and maintenance requirements, weather conditions, upstream and downstream water management schemes and many other constraints may restrict operation to other than the desired levels. In addition, operation at conditions other than those determined to provide the best hydraulic efficiency may be permitted to exist and continue due to a failure to appreciate the magnitude of the actual or opportunity costs of such operation.
While operations, engineering and management personnel may generally be aware in such situations that the facility is being operated at inefficient levels, except for commonly assigned and co-pending U.S. application Ser. No. 08/700,314, filed Aug. 18, 1996, heretofore known control systems have not provided sufficiently informative feedback relating to the actual performance costs of such operation. In particular, known hydroelectric plant control systems do not quantify inefficient hydraulic operation in economic terms that are readily meaningful to plant personnel. Consequently, correction of such inefficient operation may be delayed unnecessarily, causing the facility to incur unnecessary real or opportunity costs.
The above-identified U.S. application Ser. No. 08/700,314 discloses an improved system for monitoring and evaluating operation of a hydroelectric power generation facility by providing a realistic and continuous estimate of economic costs associated with operating the facility at other than the conditions desired for optimum hydraulic efficiency. The cost evaluation system is capable of comparing current operating conditions to predetermined or identified optimal conditions, and informing plant personnel in real-time of the economic costs of continued operation at current conditions. In addition, the monitoring system is capable of isolating the cost influence of various operating parameters independently, as well as tracking performance and accumulated performance costs, thereby allowing plant personnel to address particular facets of operation independently.
It is also generally known that operational efficiency can be affected by operating a turbine in a mode designed to satisfy environmental constraints. By way of example, hydroelectric power installations including features designed to satisfy environmental constraints by enhancing dissolved oxygen levels in the water flowing through the turbines are disclosed in U.S. Pat. Nos. 5,823,740 (issued Oct. 20, 1998), U.S. Pat. No. 5,879,130 (issued Mar. 09, 1999), and U.S. Pat. No. 5,896,657 (issued Apr. 27, 1999). Operating these turbines to enhance the dissolved oxygen level typically causes a loss of hydraulic efficiency in the facility, even though the turbines may each be operating with the gate opening and/or blade positions thought to provide optimal hydraulic efficiency. Although plant personnel may be aware that operation of the turbines to satisfy environmental constraints is resulting in hydraulic efficiency losses, the heretofore known control systems failed to provide sufficient information as to the cost of satisfying such environmental constraints in meaningful economic terms.
In addition to above-described increased operational costs resulting from hydraulic inefficiencies during turbine operation, another cost associated with turbine operation is maintenance cost. In general, turbine components as well as the turbines themselves have expected life spans that are shorter than the anticipated life span of the overall hydro installation, and thus such components and/or units must be periodically maintained and/or replaced. Rehabilitating or replacing turbine components or units typically involves substantial costs in term of both parts and labor as well as lost opportunity cost if the turbine must be shut down for the repair. This problem can be exacerbated if the turbine facility is operated under conditions that produce particularly severe stressors (e.g., excessive vibration or cavitation) known to adversely affect turbine components and result in excessive wear. That is, experience has shown that how the turbine is operated typically has a larger impact on the life of the turbine and its components than any other factor.
As with the heretofore known control systems for monitoring the costs of inefficient hydraulic operation, such control systems also have not provided plant personnel with sufficient information to know how much of the overall life of the turbine or its component is being xe2x80x9cused upxe2x80x9d or accelerated by operation under the current conditions, or the maintenance costs associated with such operation. Accordingly, correction of the conditions causing the stressful or undesirable operation may be delayed unnecessarily, causing the facility to incur real or opportunity costs due to costly, frequent or unnecessary maintenance.
Although theoretical in nature and not heretofore applied to the hydro turbine art, Rabinowicz et al. (1970) has applied a concept known as cumulative damage theory to accelerated life testing of mechanical and electromechanical systems including bearings, light bulbs, electric motors, and electric tools. Cumulative damage theory, which was originally developed in conjunction with fatigue testing of metals (Palmgren, 1924; Miner, 1945; Brook and Parry, 1969), holds that the life of a fatigue specimen, over a wide range of stresses, follows a relationship of this form:
xe2x80x83Life=A"sgr"(xe2x88x92B)xe2x80x83xe2x80x83(1);
where A is a constant of proportionality, "sgr" is the level of stress in the specimen under test, and B is a numerical constant. The results of Rabinowicz et al. suggest that cumulative damage theory is widely applicable to complex, real-world situations where the precise laws and mechanisms of deterioration are not explicitly known. The ability to evaluate the expected life of equipment under varying conditions would have enormous value in the hydro turbine art because it would allow the economic assessment and optimization of operational parameters and the cost-effective performance of condition-based, and operations-based, maintenance.
There is a need, therefore, for an improved system for monitoring and evaluating operation of a hydroelectric power generation facility that provides a realistic and continuous estimate of performance costs associated with operating the facility to satisfy environmental constraints. Moreover, there is a need for a monitoring system capable of estimating how much of the facility""s or its components"" expected life spans are being used up by continued operation under the current conditions, as well as the maintenance costs associated with such operation. Further, there is a need for a monitoring system capable of isolating the expected life and cost influences of various operating parameters independently, and of tracking present and accumulated life used up as well as maintenance costs associated with the various parameters, thereby allowing plant management to address particular facets of operation independently.
The present invention, featuring a novel technique for utilizing and presenting results from the continuous monitoring of operations for a hydroelectric power generating facility, is designed to respond to these needs. The technique may be adapted to new facilities or may be retrofitted to existing plants, typically without the need for downtime or additional instrumentation.
Thus, the invention features a method for monitoring maintenance-related information in a hydroelectric power generation facility including at least one turbine having turbine components. In accordance with the method, at least one operating parameter is monitored for a desired operating period at an operating condition. The at least one monitored parameter includes a stressor capable of affecting a life span, or mean time between failures, of the turbine or one of its components. In addition, the amount of the life span of the component or turbine used up over the operating period by operating at the operating condition subject to the stressor is calculated. The current, real-time value of the maintenance cost per unit time is also calculated.
The present invention also features a system for monitoring maintenance-related information in a hydroelectric power generation facility including at least one turbine having turbine components. The system comprises at least one sensor coupled to a controller. The at least one sensor is situated in the facility to detect actual levels of at least one operating parameter for a desired operating period at an operating condition. The at least one detected parameter includes a stressor capable of affecting a life span, or mean time between failures, of the turbine or one of its components. The controller is configured to determine the amount of the life span used up at the operating condition subject to the stressor for the operating period.
The invention also features a method for monitoring and evaluating losses in a hydroelectric power generation facility resulting from operating the facility to satisfy environmental constraints. In accordance with the method, a set of predetermined reference signals representative of desired turbine efficiencies over a range of operating levels are stored in a memory circuit. In addition, current levels of operating parameters are sensed while the facility is operating to satisfy the environmental constraints. A sensed parameter signal representative of a current turbine efficiency is then generated from the sensed levels of operating parameters. The generated parameter signal is compared to the predetermined reference signals to determine an environmental efficiency loss signal.
These and other benefits and features of the invention will be apparent upon consideration of the following detailed description of preferred embodiments thereof, presented in connection with the following drawings in which like reference numerals identify like elements throughout.